The invention relates to a method for the sampling of biphase coded digital signals in accordance with Patent claim 1. In particular, the invention also relates to a method for the central driving of the electrical loads of a lighting system, for example the operating units of the lamps, by means of biphase coded digital control signals.
When a digital signal is subject to biphase coding, each bit of the digital signal is subdivided into two half-bits having different logic states. In each bit of the signal, the first and second half-bits have different logic levels and a falling or a rising signal edge occurs between these two half-bits, depending on whether the first or the second half-bit is at the logic level xe2x80x9c1xe2x80x9d. During regular data transmission, therefore, the logic levels xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d have to alternate periodically.
In order to receive biphase coded digital signals, it is customary firstly to effect a synchronization with the edge of the start bit of the received signal and to start sampling this signal with a period duration which is shorter than the transmission duration of a half-bit. Thus, at least one sampling is effected per half-bit. The quality of this method, in particular the detection of transmission errors, improves as the number of individual samplings for each half-bit rises. With the aid of an evaluation device, an average value is formed from the individual samplings of the logic level of the half-bit and, by comparison with two threshold values, the logic level of this half-bit is determined as xe2x80x9c0xe2x80x9d or xe2x80x9c1xe2x80x9d. Although increasing the number of individual samplings improves the error detection, at the same time, however, it also increases the system loading and leads to the system slowing down in the case of so-called multitasking systems.
The object of the invention is to provide a method for the sampling of biphase coded digital signals by reception means which have at least one signal input having switchable signal edge sensitivity which requires the smallest possible number of samplings of the received signal and nevertheless ensures synchronization with the transmission and also detection of transmission errors.
This object is achieved according to the invention by means of the features of Patent claim 1. Particularly advantageous embodiments of the invention are described in the subclaims.
In the invention""s method for the sampling of biphase coded digital signals by reception means which have at least one signal input having switchable signal edge sensitivity or at least two signal inputs having different signal edge sensitivity for the reception of such signals, in order to receive such a signal
A) the signal edge sensitivity of the at least one signal input is set to a falling signal edge if its quiescent state logic level is xe2x80x9c1xe2x80x9d, and its signal edge sensitivity is set to a rising signal edge if its quiescent state logic level is xe2x80x9c0xe2x80x9d, in order to detect the beginning of a signal, or the signal input having the corresponding signal edge sensitivity is activated in order to detect the beginning of a signal,
B) sampling of the logic level of the first half-bit of the instantaneously received bit of the signal is carried out,
C) the signal edge sensitivity of the at least one signal input is set as a function of the logic level of the sampled first half-bit of the instantaneously received bit, or the signal input having the corresponding signal edge sensitivity is activated as a function of the logic level of the sampled first half-bit of the instantaneously received bit,
D) a time window (xcex94t) is prescribed during which the occurrence of the signal edge between the first and second half-bits of the abovementioned bit of the signal is expected and evaluated as permissible,
E) a check is made to determine whether the abovementioned signal edge has occurred within the prescribed time window, and, if the signal edge between the first and second half-bits has been detected within the prescribed time window, method steps B) to E) are repeated for the next bit of the signal, or the signal reception is otherwise terminated.
The method according to the invention provides only a single sampling of the signal per bit. It is wholly sufficient for just the respective first half-bit of each data bit of the signal to be sampled once in order to evaluate the signal and reliably detect errors in the coding of the signal. According to the invention, the signal edge occurring in each bit of the signal is ultilized for synchronizing the at least one signal input with the received signal and for detecting errors in the coding of the signal. The prescription of a time window during which the signal edge between the first and second half-bits can be detected limits the permissible fluctuations of the temporal bit length and thus also the permissible fluctuations of the signal transmission rate.
The method according to the invention can advantageously be applied to a lighting system which has a plurality of lamps, at least one operating unit for the lamps and at least one control unit for driving the at least one operating unit.